Re: [PATCH v2 02/31] exportfs: add new EXPORT_OP_STABLE_HANDLES flag

Christoph Hellwig
2026-01-20T07:50:34Z

On Mon, Jan 19, 2026 at 11:26:19AM -0500, Jeff Layton wrote:
> + EXPORT_OP_STABLE_HANDLES - This filesystem provides filehandles that are
> + stable across the lifetime of a file. This is a hard requirement for export
> + via nfsd. Any filesystem that is eligible to be exported via nfsd must
> + indicate this guarantee by setting this flag. Most disk-based filesystems
> + can do this naturally. Pseudofilesystems that are for local reporting and
> + control (e.g. kernfs, pidfs, nsfs) usually can't support this.

Suggested rewording, taking some of the ideas from Dave Chinners earlier
comments into account:

EXPORT_OP_STABLE_HANDLES - This filesystem provides filehandles that are
stable across the lifetime of a file. A file in this context is an
instantiated inode reachable by one or more file names, or still open after
the last name has been unlinked. Reuses of the same on-disk inode structure
are considered new files and must provide different file handles from the
previous incarnation. Most file systems designed to store user data
naturally provide this capability. Pseudofilesystems that are for local
reporting and control (e.g. kernfs, pidfs, nsfs) usually can't support this.

This flags is a hard requirement for export via nfsd. Any filesystem that
is eligible to be exported via nfsd must indicate this guarantee by
setting this flag.